Process of casting light metals in sand molds



Sept. 6, 1932. E. PLAYER 1,876,073

' l PRocEss oF CASTING LIGHT METALS'IN s-AND MOLDs Filed sept. 19. A1929 l' Yagi l azwmfywger f l IN VEN TOR.

ATTORNEYS.

ency to warp and to crac Patented Sept. 6, 1932 UNITED STATES PATENT .OFFICE EDWARD PLAYER, OF ASTIJEY, ENGLAND, ASSIGNOR, BY MESNE ASSIGNMENTS, T0 MAGNESIUM DEVELOPMENT CORPDRATION, A CORPORATION 0F DELAWARE PROCESS on CASTING LIGHT METALS TN SANT) -MOLDS Application led September 19, 1929, Serial No. 393,844, and in Germany September 19,1928. i

This invention relates to the casting of metals in sand molds. l

.When casting metals into sand molds it is generally considered necessary, especially in of the casting in that particular section, thus preventing the setting up of internal stresses and the formation of cracksand similar de- Vfects in the casting on further cooling. The

necessity for employing chills in sand molds is particularly pronounced in the casting of light metals such as aluminum and mag.

nesium,'these metals havin a stronger tendowing to their comparatively high shrinkage. As the molten metal does not easily'reston the chills when the latterare coldit is further necessary to heat the chills before filling the mold with metal so as to ensure a flawless surface of thecastingsin these places. This heating is generally effected by means of a suitable burner or blow-pipe, the jet being directed successively on the different chills.

While this method, although apparently b primitive, yields lvery good-results in'the case of smaller castings, it has lproved far from reliable when larger castings provided, sometimes, withfrom fty to several hundred chills, are concerned. In such cases, the surface of the casting frequently displays blowholes and similar defects in the place of the chills. Attempts to remove these deliciencies of the method by a more intense heating of the chills and by the application of various blackwashes were of small avail and did not result in rendering the production of perfect castings reliable on a commercial scale.

These difhculties, while existing also to some extent when casting aluminum, appear seriously enhanced in the case of magnesium and its alloys, which are usually cast into green sand molds impregnated with volatili;- able protective substances, as a more intense heating of the chills causes these substances to evaporate in the sections of the sand surrounding the chills and'this frequently gives occasion to a detrimental reaction between the sand lof the mold and the `molten metal. Moreover, magnesium and its high percent? age alloys are .liable to react chemically with any sensible moisture condensed on the surface of chills.

A/closer investigation of the causes of these diii'culties by applicants has now revealed that-they must be attributed to differences in the temperature of the various chills. These dilf'erences arise from the successive heating of the individual chills by means of burners or the like, which procedure allows the chills first heated to cool downto lower temperatures,'mostly:by radiation, while other chills are still being heated. On closing the mold the moisture contained in the sand surrounding the hottest chills evaporates and pervading the interior of the mold, is condensedon such chills as, although still warm, have cooled down in the meantime. On contact with the molten metal, these condensations of moisture give rise to blow-holes or similar defects in the surface of the casting.

'It follows from the result of these investigations that the heating of thechills should be carried out in4 such a manner that all the chills in the mold are simultaneously and uniformly heated.

' Experiments along these lines have resulted in the productionof perfect light metal castings, even when very large and provided with a great number of chills. They have further elicited the fact that the temperature range within which the chills must be heated sov one of the apertures or' the mold (such as risers or runner bushes). g

In the accompanying drawing a. vertical section of a suitable apparatus for carrying out the present invention is represented in a diagrammatic manner. a designates the sand mold, whereas b represents the free space corresponding to the outlines of the finished casting. c are chill plates inserted at two points of the mold where the nature of the casting requires enhanced cooling. One end of a suitable mouth-piece e is detachably fitted to one of the gates d of the mold, whereas its other end is connected with the tap g of a suitable air heating device (not shown) by means of a flexible tube f. The heated air is supplied to the mold by means of the mouth piece e and, after circulating in the hollow space b, issues from the mold partly by the lfree gate d, partly by the crevices in the sand of the mold. When the chill plates c have uniforml attained the desired temperatures, the mout piece e is removed from the' mold which is thereupon immediately filled with the molten metal in the usual manner.

In a process of castin light metals in green sand' molds provide with a plurality of local chill plates, the preliminary step of simultaneously and/uniformly heating said chllls to a temperature within the range between about 50 and 100 C., by passing a current of heated air through the mold for some time prior to casting.

In testimony whereof I have hereunto set my hand.

EDWARD PLAYER. 

